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John W. Edwards

Bio: John W. Edwards is an academic researcher from Langley Research Center. The author has contributed to research in topics: Transonic & Aeroelasticity. The author has an hindex of 13, co-authored 31 publications receiving 799 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, a transonic small perturbation potential equation was used to determine transonic flutter boundaries versus Mach number and angle of attack for NACA 64A010 and MBB A-3 airfoils.
Abstract: Transonic aeroelastic solutions based upon the transonic small perturbation potential equation were studied. Time-marching transient solutions of plunging and pitching airfoils were analyzed using a complex exponential modal identification technique, and seven alternative integration techniques for the structural equations were evaluated. The HYTRAN2 code was used to determine transonic flutter boundaries versus Mach number and angle-of-attack for NACA 64A010 and MBB A-3 airfoils. In the code, a monotone differencing method, which eliminates leading edge expansion shocks, is used to solve the potential equation. When the effect of static pitching moment upon the angle-of-attack is included, the MBB A-3 airfoil can have multiple flutter speeds at a given Mach number.

169 citations

Proceedings ArticleDOI
15 Jun 1998
TL;DR: The motivation for CA and the elements of one type of the analysis or simulation process are briefly reviewed in this article, and the need for streamlining and improving the overall process to reduce elapsed time and improve overall accuracy is discussed.
Abstract: The motivation for Computational Aeroelasticity (CA) and the elements of one type of the analysis or simulation process are briefly reviewed The need for streamlining and improving the overall process to reduce elapsed time and improve overall accuracy is discussed Further effort is needed to establish the credibility of the methodology, obtain experience, and to incorporate the experience base to simplify the method for future use Experience with the application of a variety of Computational Aeroelasticity programs is summarized for the transonic flutter of two wings, the AGARD 4456 wing and a typical business jet wing There is a compelling need for a broad range of additional flutter test cases for further comparisons Some existing data sets that may offer CA challenges are presented

93 citations

Proceedings ArticleDOI
01 Jan 1993
TL;DR: In this article, a viscous-inviscid interactive coupling method is described with the aim of allowing time-accurate computation of unsteady transonic flows involving separation and reattachment.
Abstract: A new viscous-inviscid interactive coupling method is described with the aim of allowing time-accurate computation of unsteady transonic flows involving separation and reattachment. A lag-entrainment integral boundary layer method is used in conjunction with a transonic small disturbance potential code. The solutions are coupled with a novel variable gain, integral control method for the boundary layer displacement thickness. Efficient and robust computations of steady and unsteady separated flows, including steady separation bubbles and self-excited shock-induced oscillations, are presented. The buffet onset boundary for the NACA 0012 airfoil is accurately predicted and shown computationally to be a Hopf bifurcation. Shock-induced oscillations are also presented for the 18 percent thick circular arc airfoil. The oscillation onset boundaries and frequencies are accurately predicted, as is the experimentally observed hysteresis of the oscillations with Mach number; this latter stability boundary is identified as a jump phenomenon.

89 citations

Proceedings ArticleDOI
01 Mar 1987
TL;DR: The importance of mixed attached and separated flow modeling for aeroelastic analysis is discussed and recent calculations of periodic aerodynamic oscillations for an 18 percent thick circular arc airfoil are given.
Abstract: Computational methods for unsteady transonic flows are surveyed with emphasis on prediction. Computational difficulty is discussed with respect to type of unsteady flow; attached, mixed (attached/separated) and separated. Significant early computations of shock motions, aileron buzz and periodic oscillations are discussed. The maturation of computational methods towards the capability of treating complete vehicles with reasonable computational resources is noted and a survey of recent comparisons with experimental results is compiled. The importance of mixed attached and separated flow modeling for aeroelastic analysis is discussed, and recent calculations of periodic aerodynamic oscillations for an 18 percent thick circular arc airfoil are given.

84 citations

Journal ArticleDOI
TL;DR: The current status of computational methods for unsteady aerodynamics and aeroelasticity is reviewed in this paper, where the key features of challenging aero-elastic applications are discussed in terms of the flowfield state: low-angle high speed flows and high-angle vortex-dominated flows.

61 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, two algorithms for the solution of the time-dependent Euler equations are presented for unsteady aerodynamic analysis of oscillating airfoils for use on an unstructured grid made up of triangles.
Abstract: Two algorithms for the solution of the time-dependent Euler equations are presented for unsteady aerodynamic analysis of oscillating airfoils. Both algorithms were developed for use on an unstructured grid made up of triangles. The first flow solver involves a Runge-Kutta time-stepping scheme with a finite-volume spatial discretization that reduces to central differencing on a rectangular mesh. The second flow solver involves a modified Euler time-integration scheme with an upwind-biased spatial discretization based on the flux-vector splitting of Van Leer. The paper presents descriptions of the Euler solvers and dynamic mesh algorithm along with results which assess the capability.

783 citations

Journal ArticleDOI
TL;DR: In this paper, the authors review the development of new reduced-order modeling techniques and discuss their applicability to various problems in computational physics, including aerodynamic and aeroelastic behaviors of two-dimensional and three-dimensional geometries.

732 citations

Journal ArticleDOI
TL;DR: A review of the state of the art and present status of active aeroelastic rotor control research for wind turbines is presented in this paper, where the authors discuss the potential of load reduction using smart rotor control concepts.

491 citations

Journal ArticleDOI
TL;DR: In this paper, a method for constructing reduced-order models of unsteady small-disturbance e ows is presented, using basis vectors determined from the proper orthogonal decomposition (POD) of an ensemble of small-disorderance frequency-domain solutions.
Abstract: A new method for constructing reduced-order models (ROM) of unsteady small-disturbance e ows is presented. The reduced-order models are constructed using basis vectors determined from the proper orthogonal decomposition (POD) of an ensemble of small-disturbance frequency-domain solutions. Each of the individual frequencydomain solutions is computed using an efe cient time-linearized e ow solver. We show that reduced-order models can be constructed using just a handful of POD basis vectors, producing low-order but highly accurate models of the unsteady e ow over a wide range of frequencies. We apply the POD/ROM technique to compute the unsteady aerodynamic and aeroelastic behavior of an isolated transonic airfoil and to a two-dimensional cascade of airfoils.

352 citations